1. Field of the Invention
The present invention relates to a method for providing IP (Internet Protocol) multicast service using a virtual LAN (Local Area Network), and more particularly to a method for providing IP multicast service using a virtual LAN, wherein the method can provide efficient multicast service in a very high-speed network and rapidly process data by applying the virtual LAN to the IP multicast service.
2. Description of the Prior Art
Generally, multicasting is a data transmission method capable of efficiently employing resources of a network, whereby a specific group is organized and data is broadcast to a corresponding group so that the number of data transmissions by one sender can be reduced. Thus, the sender can send data to countless receivers through one data transmission, and the data is prevented from being sent to a destination if the destination does not want to receive the data, thereby preventing unnecessary network use (RFC 1112: Host Extensions for IP Multicasting, S. Deering, August 1989). Moreover, IP multicasting can maximally utilize bandwidth, maximally reduce a sender load, and efficiently employ the resources of the network. However, there is a problem in that, because the IP multicast necessarily needs software to carry out operations associated with a lower-order physical layer and a higher-order network layer, the IP multicast cannot acquire a desired bit rate in a very high-speed network. Moreover, there is a disadvantage in that all equipment in the network (including router, etc.) should support the IP multicast.
On the other hand, a VLAN (Virtual Local Area Network) is restricted to a configuration of a physical network by Network Administrator. In the VLAN, a logical network between network components can be flexibly formed and a bit rate is very high. That is, where a new network is configured, the network does not have to be physically configured, thereby saving costs for physically configuring the network. Through a VLAN function, the new network can be logically configured without any physical variation. The VLAN includes a port based VLAN, a layer 2 based VLAN and a policy based VLAN according to a user's network (IEEE 802.1Q, Virtual Bridged Local Area Network, IEEE 802.1, December 1998). Because the VLAN is implemented by hardware, it can achieve a relatively high bit rate. As the user cannot change or re-configure the network, only Network Administrator is able to change it. Furthermore, the VLAN is based on a protocol such as a GMRP (GARP Multicast Registration Protocol) for multicast communication, but the protocol support only single multicast address, so that this protocol is not able to make multiple multicast addresses.
FIG. 1 roughly shows a conventional IP multicast structure. Referring to FIG. 1, in a case of the conventional IP multicast, session information is transferred through an SDP (Session Description Protocol) and a host as a member desiring to join or leave a group can join or leave the group associated with a “JoinHostGroup/LeaveHostGroup” process through an IGMP (Internet Group Management Protocol). As described above, the member's joining or leaving is managed by an IGMP router 11 as a multicast router through the IGMP. Thus, data is sent to only joiners in the groups of a network A 12 and a network B 13. In this method, IGMP routers 11 should necessarily carry out all operations associated with OSI (Open Systems Interconnection) 1st˜3rd layers 14. Where the amount of traffic increases and the joining or leaving of group members frequently occurs, there is a problem in that the IGMP routers 11 should carry a heavy load.
On the other hand, FIG. 2 roughly shows a conventional VLAN structure. The VLAN forms one group by designating a sub-network management group between network devices through a GVRP (GARP VLAN Registration Protocol) 22. That is, the group formed through the GVRP 22 can be identified as a group formed by the VLAN. Accordingly, data sent from the sender 21 is broadcast to the group formed through the GVRP 22. Since the GVRP 22 is a hardware-based protocol, a bit rate in the GVRP 22 is very high, but the user cannot readily intervene in the GVRP 22 and only a network device manager can directly intervene in the GVRP 22.
On the other hand, as a prior art patent associated with an IP multicast/VLAN, there is U.S. Pat. No. 6,112,251 entitled “Virtual Local Network for Sending Multicast Transmission to Trunk Station”, Anil G. Rijhsinghani, August 2000. As disclosed in the prior art patent, both IP multicast information and VLAN information is contained in a protocol header so that network equipment can use only information capable of being processed by its own equipment and therefore have flexibility. FIG. 3 shows a structure of the IP multicast/VLAN disclosed in the prior art patent. Where a message having the protocol header containing both IP multicast information and VLAN address information is sent to a network in FIG. 3, network equipment 31, 32 and 33 selects and processes desired information between the IP multicast information and the VLAN address information. However, there is a problem in that a multicast group manager is not considered in the IP multicast/VLAN and that the network equipment should support a specific protocol disclosed in the prior art patent.
With regard to a combination of the VLAN and the IP multicast, only a protocol has been proposed, and structures and detailed operations of management programs have not been yet proposed. In particular, upon combining the VLAN and the IP multicast, problems associated with a network's transmission speed and global utility should be addressed.